In recent years, there has been proposed a system, which is a so-called microgrid in which a distributed power supply is provided to an electric power system in a particular area to meet most of demands for electric power in the area. In such a system, in order to maintain a balance between supply and demand of electric power, there is known a technique in which power storage equipment is provided and charging and discharging of a storage battery are controlled in accordance with a power flow from the electric power system (PTL 1).
There is also known, as another conventional art, a technique in which whether electric power generated from a solar power generator is sold to a system side or is stored in an energy storage device is switched in accordance with a state of voltage suppression that has been previously generated on the system side (PTL 2).